This invention relates to a method of securing plugs (particularly but not exclusively screw-receiving plugs) in oversized holes formed in fixtures,xe2x80x94thereby to enable, for example, screws, bolts or even nails to be secured in a fixture. The invention also provides means for use in carrying out that method.
In the description and claims that follow hereafter, the term xe2x80x9cscrewsxe2x80x9d will include xe2x80x9cboltsxe2x80x9d as well, and will encompass screws that have screw-threaded cylindrical shanks as well as screws having screw-threaded conical shanks.
Devices and appliances are frequently secured to a supporting fixture or structure (e.g. a wall, cabinet or panel) by means of screws. In some cases, such screws cannot be screwed directly into the structure because of the nature of the material of the structure, but instead are inserted into a plug of a screw-receiving material that has been previously inserted in a frictionally-engaging manner in a hole preformed in the structure. Driving the screw into the plug tends to radially enlarge the plug, thus causing the frictional engagement of the plug with the structure to intensify and thereby resist both longitudinal and rotational displacement of the plug within the hole as the screw is driven home to firmly secure the device or appliance to the structure.
Difficulties can arise in preforming the hole in the structure, for examplexe2x80x94where the material of the structure is not homogeneous, or is easily eroded non-uniformly during the drilling of the hole. As a result, the hole is sometimes larger than desired (and/or mis-shapen) for the size of the plug intended to be engaged therein. This happens for example where the hole is being drilled in mortar bonds between bricks.
In such cases remedial measures may include using a larger plug to receive the plug or screw originally intended to be used, or simply a larger screw; or alternatively filling the over-sized hole with a suitable homogeneous plastic filler material, and then redrilling the necessary plug-receiving hole in the filler material after it has hardened.
Unfortunately, the latter procedure unduly prolongs the time of securing the screw since the hardening of the filler material requires a relatively long setting time before it can safely carry a load, because of the bulk of the filler material to be hardened, and its almost complete enclosure in the hole. Suitable plastic fillers include epoxy resins, but they are relatively expensive, require special mixing procedures, have long hardening times, and can present problems in safe handling and storage, e.g. dermatalogical problems for the user.
The present invention seeks to provide a method and means for enabling plugs (e.g. screw-receiving plugs) to be secured in circumstances where the preformed hole is unfortunately enlarged beyond the intended size, which method and means do not require resort to the use of a larger plug or screw, or a long filler-hardening time.
According to the present invention, a method of securing a plug, for example a screw-receiving plug, in an over-sized preformed hole comprises the steps of: (a) providing at least one piece or a loosely-woven fabric carrying consolidated thereon a quick-setting filler material, which fabric piece is sized to envelop at least circuferentially the plug intended to be used; (b) enveloping the plug at least circuferentially in the fabric piece; (c) causing activation of the filler material thereby to initiate hardening and eventual setting of the filler material; and (d) inserting the enveloped plug without delay in the oversized hole in a manner such as to ensure filling of the oversized hole with the enveloped plug. After the elapse of a relatively short filler-hardening time, the intended screw (or nail) may be inserted in and screwed into the plug.
By the term xe2x80x9cloosely-woven fabricxe2x80x9d is meant any fabric whether woven or knitted which is capable of constituting an open matrix material or substrate on to which the filler material may be consolidated or impregnated. This term shall be construed broadly in this manner wherever appropriate in this description and in the appended claims. Such a fabric may comprise for example a gauze material or a leno weave material.
Where the filler material requires activation by air, as in the case of some synthetic resin filler materials e.g. a polyurethane resin, activation will commence at the moment of releasing the fabric from an airtight storage container, so that enveloping the plug in the fabric occurs shortly after air activation has started.
Where the filler material requires activation by water, as in the case of one preferred filler material, for example plaster of Paris, activation is achieved by wetting the enveloped plug with water.
Enveloping the plug in the filler impregnated-fabric provides a reliable method of ensuring that sufficient filler material is carried with the plug into the hole to its fullest extent. This is extremely difficult to achieve without the fabric carried on the plug, so that safe securing of the plug in the oversized hole is then unpredictable and unreliable.
Water-activated filler materials have the advantage compared with the air-activated filler materials that they are relatively cheap and plentiful, and give rise to few dermatoligical problems for the user.
The preferred water-activated filler material comprises plaster of Paris, though any other suitable filler material manufactured from gypsum will suffice.
If desired, the filler material may have mixed with it short, strength-enhancing fibres or glass, carbon or other suitable material.
The fabric piece may be in the form of a tape or strip, and be wound on to the plug thereby to envelop it circumferentially. Alternatively, the fabric piece may be circular in shape, or substantially so, and be placed over the closed end of the plug and then smoothed longitudinally along the plug to the open end thereof so as to envelop it circumferentially in a substantially uniform manner.
According to a further aspect of the invention, there is provided for use in the method of the present invention a piece of a loosely-woven fabric carrying consolidated thereon a quick-setting filler material, which fabric piece is in the form of a tape which is transversely weakened at positions spaced along the tape so as to enable ready detachment of successive pieces as desired for use in practising a method according to the present invention.
Said filler material may, if desired, have mixed with it short, strength-enhancing fibres of glass, carbon or other suitable material.
The tape may be wound in the form of a roll, or alternatively it may be folded upon itself at said weakened positions in a fan-fold manner.
Where air-activated filler material is used, it is essential to enclose the fabric tape in an air-tight enclosure to prevent activation until the tape is about to be put into use.
Where water-activated filler material is used, it is necessary to enclose the fabric tape in a watertight enclosure so as to ensure its storage in a dry condition prior to use.
The present invention also provides for use in the method of the present invention an enclosure containing a selection of separate filler-carrying fabric pieces of substantially circular or rectangular configuration, which pieces may be all of one size, or of various sizes to suit different plug sizes.
Preferably, the airtight and watertight enclosures incorporate appropriate resealing means for maintaining respectively the airtightness and watertightness of the respective enclosures, and contain or carry printed instructions setting out the manner of using the fabric pieces in accordance with the present invention.
According to another aspect of the present invention, there are provided for use in carrying out the present invention ready-made (pre-prepared) units each comprising a said plug having secured therearound a sleeve (preferably closed at one end) of a said loosely-woven fabric carrying consolidated thereon a said quick-setting filler material, with or without said strength-enhancing fibres. Such fabric may be retained on the plug by being impaled on radial, retaining projections such as are commonly formed on screw-receiving plugs, or by an adhesive substance.
Other features of the present invention will appear from a reading of the description that follows hereafter and of the claims appended at the end of that description.
Various methods incorporating the present invention, of securing screws in a fixture, and means for use in practising those methods, will now be described by way of example, and with reference to the accompanying drawings, in which: